As is known, upholstered cushions in general, and those with fillings of wool, down, and expanded synthetic fiber flock in particular, used as backrests are suitable for numerous uses owing to the complete freedom of movement and adaptation which the filling permits within the containing cover. They consequently have the advantage of making a rigid or semi-rigid supporting plane, for example the backrest of a chair, sofa or armchair, soft and agreeable, and also of imparting uniformity to areas disposed at an angle to each other or situated at different levels, as a result of the type of filling which is free to move to compensate for various types of recesses and differences in level. However, they also have both practical and aesthetic disadvantages, since, after their deformation, they are not always able to return to the original extended and full shape, as a result of which they create disagreeable aesthetic effects and a situation of disorder which has to be remedied by intervening manually to redistribute the filling material within the cover.
In the case of backrests consisting of large and small mattresses, equally spaced stitchings are provided to keep the filling uniformly distributed within the cover as long as possible. Such stitchings effectively divide the mattresses into the same number of sections of small dimensions.